What is A5?

A5 is a commonly used standard of paper due. The ISO 216 standard defines A5 size to be 148mm × 210mm, which is also exactly half the size of an A4.

Usually A5 sized paper will be used for booklet printing, flyers, leaflets, advertisements, or if on heavier stock, it can be scored and folded to make A6 sized greeting cards.

In the ISO paper size system, the height-to-width ratio of all pages is the square root of two. In other words, the width and the height of a page relate to each other like the side and the diagonal of a square. This aspect ratio is especially convenient for a paper size. If you put two such pages next to each other, or equivalently cut one parallel to its shorter side into two equal pieces, then the resulting page will have again the same width/height ratio.